The present invention relates to an apparatus for producing rubber mixtures, including a ram kneader that operates in a batch process for producing a master batch. Disposed below the ram kneader is a ram-less kneader that also operates in a batch process, is designed for admixing reactive additives, and serves for producing the final mixture and for cooling the mixture. The master batch is transferable from the ram kneader to the ram-less kneader without intermediate storage thereof. A surface wear protection layer is provided for the active, inwardly disposed kneader surfaces that come into contact with the rubber mixture, and cooling means are provided for the rotors and the casings of the two kneaders that accommodate the same.
In order to prevent premature wear of the aforementioned active surfaces, and in particular of the rotor surfaces, these surfaces are provided with a surface wear protection layer that contains cobalt, tungsten, chromium and carbon, with these materials being used in combination with one another, for example as STELLITE. With today's technology, these special layers are generally indispensible; they are used for both the master batcher and the final mixer.
However, peculiarities arise with the aforementioned apparatus, because the mixture that is obtained directly from the master batcher without intermediate storage must be rapidly and adequately cooled and final mixed in the ram-less kneader.
Furthermore, the present invention proceeds from the recognition that in the final mixer, of particular significance to the aforementioned ram-less kneader is the speed at which the empty kneader cools, and the cooling effect during the final mixing process. The cooling speed of a just-emptied kneader is important because the cooler that the kneader is, the more rapidly can the master batch be cooled. The cooling effect during the mixing process is important, because with a good cooling, the reactive additives can be more aggressively mixed and hence more reliably blended.
It is therefore an object of the present invention to improve an apparatus of the aforementioned general type in such a way that the master batch that is obtained is rapidly cooled, and the final mixing process can be rapidly and reliably carried out without having to worry that the mixture will, for example, start to react or vulcanize.